SNX-111 is a voltage-sensitive calcium channel blocker that specifically blocks neuronal (N-type) calcium channels. These channels are found in highest density within the substantia gelatinosa of the dorsal horn, where blockade of calcium influx has been shown to produce analgesia. The present study is designed to evaluate the safety and efficacy of low dose, intrathecal SNX-111 in relieving chronic, nonmalignant pain. Drug will be delivered via implanted intrathecal infusion system. Dose will be titrated weekly over 7 weeks until analgesia is achieved or until intolerable side effects occur.